AD-Related Administrative Supplement for DP1 DA041722, ?Aberrant protein S-nitrosylation mediates synaptic and neuronal toxicity in hiPSC-based models of Lewy Body Dementia (LBD)? SUMMARY Lewy body dementia (LBD), classified as an Alzheimer?s disease (AD)-related dementia, represents the second most common form of neurodegenerative disease after AD in patients above 65 years of age. The key pathological hallmark of LBD entails accumulation of a-synuclein (?Syn) inclusions, although amyloid-? (A?) and tau pathologies are also typical, suggesting that there are common pathways contributing to dementia in both LBD and AD. In fact, in LBD and AD brains, synaptic injury and neuronal damage result, at least in part, from excessive generation of reactive oxygen and nitrogen species (ROS/RNS) engendered by toxic subspecies of ?Syn and/or A?. We were the first group to show that aberrant protein S-nitrosylation (forming SNO-proteins), via RNS (e.g., nitric oxide [NO]) generation, results in synaptic/neuronal damage. Similar to our findings in the parent DP1 grant in human postmortem brains from patients with HIV-associated cognitive disorder with methamphetamine drug abuse (HAND/meth), for this supplemental proposal we present evidence for aberrantly S-nitrosylated proteins in LBD hiPSC models and LBD human brain. Hence, this supplemental application relates to the parent DP1 grant; moreover, the new work complements but is totally distinct from our work on AD human iPSCs and AD brain in a prior supplement to the parent NIDA DP1 award. As an example, our preliminary data provide evidence that mitochondrial-related protein S-nitrosylation of PINK1, MEF2C and Drp1 plays a causative role in disease- related damage in LBD. Specifically, we demonstrate that prevention of these aberrant protein S-nitrosylation reactions ameliorates the disease process, largely abrogating mitochondrial dysfunction, synaptic damage, and neuronal loss in both cell-based and animal models manifesting misfolded ?Syn. Accordingly, we propose the following Specific Aim for this Supplemental Application: Specific Aim 1: To determine the effects of oligomeric ?Syn and A? on SNO-PINK1/SNO-MEF2C/SNO- Drp1?mediated synaptic dysfunction and neuronal cell death in hiPSC-derived neuronal culture models of LBD. We will introduce non-nitrosylatable mutant PINK1, MEF2C, or Drp1 via CRISPR/Cas9 in order to test whether SNO-PINK1, SNO-MEF2C, and SNO-Drp1 contribute in a causal manner to synaptic injury and neuronal cell death. Importantly, we will compare the effects of oligomeric ?Syn/A? on hiPSC-derived cortical neurons vs. A9 dopaminergic neurons since LBD may preferentially affect cerebrocortex over substantia nigra, respectively.